


The Tree Fell Down; Just Plant the Apple

by ohjustdisarmalready



Category: Undertale (Video Game)
Genre: Alphys knows about Resets, Fear of Discovery, Fear of doctors, Gen, Happy Ending, Major Character Undeath, Memory Loss, Past Character Death, Post-Undertale Pacifist Route - "I want to stay with you.", Sans (Undertale) Has PTSD - Post-Traumatic Stress Disorder, actually assume everyone is traumatized, feat. me pushing my pro vaccine agenda on sans undertale, found family fluff, sans & toriel is distinctly not romantic. sorry soriel ppl, they got better tho, toriel has PTSD
Language: English
Status: Completed
Published: 2020-12-04
Updated: 2020-12-04
Packaged: 2021-03-09 19:19:41
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 15,255
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27881374
Author URL: https://archiveofourown.org/users/ohjustdisarmalready/pseuds/ohjustdisarmalready
Summary: Toriel wants Frisk to see a doctor. Sans thinks she should maybe not worry so much.Frisk wants to not see a doctor. Toriel thinks that they should be a little more concerned for their health.Sans mostly wants Frisk to not wander off and climb some other mountain and fall and die in a hole somewhere where nobody knows where they are and unravel the timeline and-...and Alphys thinks a whole lot of things.
Relationships: Alphys & Sans (Undertale), Frisk & Sans (Undertale), Frisk & Toriel (Undertale), Sans & Toriel (Undertale)
Comments: 16
Kudos: 58





	The Tree Fell Down; Just Plant the Apple

**Author's Note:**

> Everyone rags on Sans for being a terrible protector, but tbh he doesn't do so bad? Papyrus is totally nonlethal, he shows up and distracts Undyne in Hotland so Frisk can get across the bridge, as far as he knew Alphys had the Mettaton fight under control...I mean he didn't go above any beyond by any means, but he did pretty okay. Especially considering that protecting Frisk is probably treason, and Sans might or might not be some kind of judge/monster law something-something.
> 
> Anyway that aside I think it's hilarious to have Toriel thinking he was _much_ more openly involved than he actually was

Toriel’s history with human children leads her to be…protective. And somewhat fretful. She is aware of this. Fear—the fear that she may one day lose all of her loved ones in one horrible moment, only to face an interminable drag of doomed uncertainty before they are truly dead—has become a part of who she is.

The feeling is not even limited to human children, at this point. Her dear friend Sans’s singular HP and near-nonexistent DEF stat have led to some friction before, when she cannot fathom why he acts as if nothing can touch him. A single irritated human happening to touch him with any intent could kill him instantly. He knows this. She knows this. But, infuriatingly, he refuses to worry about it at all.

His brother, too—Toriel can understand why Sans is so proud of Papyrus, and having met him in person, she can’t help but be charmed, too. Charmed and concerned.

Papyrus is a wonderful monster, but he has a tendency to not look before he leaps, and Toriel cannot help but fear him running into danger with a smile on his face. He has always been able to turn truly concerning situations around and come out of them with new friends, but what if he can’t? What if a day comes when no one will listen to him?

Sans is more worried about people taking advantage of Papyrus’s desire to please his friends in order to make him do something that wouldn’t be in his best interests. Privately, very privately, Toriel does not think that Sans is in a position to judge on that count. After all, Sans was the one who agreed to commit treason for a woman he’s never met on the basis of bad jokes.

Toriel had not thought of it that way when she asked him to watch over and protect the next fallen human. She had not thought about what it would mean for him at all, on the other side of the door in the kingdom of monsters. She had thought, instead, of her children, each dead and gone, their bodies no doubt tossed aside or thrown into magma in the greedy quest for their SOULs.

She had been all but lost in her grief and fear, and her only thought was to ask this monster behind the door for his best mercy, in hopes that he may falter for a moment when the final SOUL inevitably left Toriel’s protection.

She had not expected him to agree, not really; she had only hoped that he would remember a mother’s plea for her child’s safety and maybe, possibly forestall the killing blow. Just for a moment. Just to let her child survive a second longer. Past a certain point, she hadn’t even been talking to Sans so much as addressing the kingdom she used to lead and cherish, through the only monster who would listen to her.

And then, wonder of wonders, Sans did agree. He made a promise, even, to watch the next human and protect them. Somehow, knowing nothing about her, between one joke and the next, Sans had put his faith in her; and that simple trust refused to die. And though she hadn’t intended to, Toriel took advantage of his compassion.

She does not regret it. She cannot. Because the end result was that Frisk survived. Because Toriel _worries_ so desperately for her children, each and every one of them, as they left her one by one to be cut down by her one-time love. Because Toriel would do—would have done—anything to protect them.

It is too late to be of any use now, for all but one of them, but Toriel desperately wants to keep Frisk safe.

She is also aware that Frisk, her youngest and only surviving ward, is highly independent and prefers not to be fretted over.

Now that the Barrier is gone and they all live on the Surface, there is a sense of loving puzzlement from her child. Frisk doesn’t seem to know quite what to do whenever she insists that they go to bed at the same time every night, and when she walks them to school on Wednesday and Thursday mornings.

Perhaps it is silly, after their trip through the entire Underground without her guidance. But Undyne only works Mondays, Tuesdays, and Fridays, so Toriel goes in late twice a week so that Frisk will not have to walk to school alone. She cherishes those mornings like they’re warm spun glass in her hands.

The first time Frisk realized that she was arriving at work at a different time in order to accompany them, they’d given her one of the most bewildered faces she’s ever seen them make. They’d asked no less than a dozen times if she was sure she wanted to go in late, and assured her a dozen more that they could get there on their own perfectly safely, if Toriel should prefer not to accompany them. Toriel knows that she is smothering them, just a little, but she insists on keeping those perfect mornings, and she hopes that they will not begrudge her for it.

Wherever she can convince herself to, Toriel tries to grant Frisk their freedom, and tries not to overstep—she is their caretaker, but not truly their mother. No matter how much she would like to be. They may have another parent, a human parent, who will come to take them away from her one day; one day, they may decide that they would be happier elsewhere and move on.

There is no telling when a child might disappear from one’s life.

It is only luck and Frisk’s love for her that may grant Toriel a warning before they leave, on that dreaded day that she hopes lies far and away in the future. It is only luck and Frisk’s love for her that grant her the precious time she does have with them now. So Toriel _tries_ : she tries not to be too restrictive, tries not to hold on too tight, tries to lay her selfishness aside for the sake of her child. She tries, and she hopes that Frisk will never come to resent her for keeping them.

Sans says that she worries too hard, that Frisk adores her and couldn’t be pried away with a crowbar, but Toriel has caught him more than once dropping by at odd hours just to check in on Frisk, as if to make sure they haven’t disappeared, that they’re still breathing. As if Sans, without ever having had or lost any children of his own, still somehow understands the fear that one’s entire world will drop out from under them.

She is not certain what exactly befell Frisk during their trip through the Underground—she suspects that the tales told to her are heavily edited to only include the best and safest parts of their adventures—but she is glad that Sans was there to protect them. She shudders to think of what might have happened had they had to go it alone.

Toriel fears the thought of so many things that could happen to Frisk.

She fears most of all that they will fall ill.

Of all her fears, that one is the strongest and the most practical. There is no more need for their SOUL, and so no need to fear that a monster will harm them; and few humans hate monsterkind enough to incite violence that Frisk could be caught in.

But Toriel fears that she will wake up one day to a wobbling voice telling her that her child will not leave bed. She fears watching helplessly as they cannot convince themself to eat monster food to aid in their recovery. She no longer has her beloved son here to sneak treats to them that they will consent to eat. Her husband is not the man she thought he was. If Frisk were to fall ill, their many friends would want to help…but Toriel would still be alone.

She fears watching her child waste away, dying by minutes in front of her very eyes. It cannot happen again. Never again. Never to Frisk.

Luckily, Frisk is a very healthy child. They walk in a slightly clumsy, shambling way, but they do walk. They barely sleep and never stay in bed longer than she can make them. They never seem to have trouble playing with the other children. Monster children are able to run faster than Frisk, who never runs under any circumstance, but they always catch up eventually.

Despite their sleepy eyes, Frisk is the furthest thing from lethargic and pained. Toriel is deeply, frantically grateful for this, every day.

That does not excuse negligence with their health, though. Toriel makes sure to give Frisk plenty of food heaped with healing magic, and serves human food as well as monster food for most meals. Frisk only ever picks at human food and pushes it around their plate, but Toriel makes sure that it’s always an option for them. She walks with them and teaches them to ensure a healthy mind, and watches carefully to heal them whenever they should get hurt.

All of these things are her responsibilities as a caretaker; responsibilities she’s happy to fulfill. Having a child in her home once more is more than enough reward for the small efforts she must put forth, and Frisk is such a self-reliant child.

One more responsibility, though, is more difficult than all of the others put together.

Frisk _must_ remain healthy. And to remain healthy, they must visit a doctor.

Toriel is nearing the end of her rope.

“My child,” she says, forcefully, as soon as Frisk opens the door after school. “Give me your backpack and keep your shoes on. We have an appointment to make in town.”

Frisk looks puzzled, obediently handing over their backpack for Toriel to hang on its hook and waiting just inside the door. Normally Toriel wouldn’t be home yet on a school day, but desperate times have called for desperate measures. She holds Frisk’s hand and hustles them down the walk.

“OH! GOODBYE AGAIN, FRISK!” calls Papyrus from his car, having just dropped Frisk off.

Frisk waves goodbye, but doesn’t get to stay and chat as Toriel strides with purpose down the way. Their hand is cold as usual in hers. She really ought to teach Papyrus how to turn the air conditioning in his car off.

The city of Forever Home is growing by the day, but Toriel lives near the center of it, simply by virtue of it having grown around her. It does not take long at all to bring Frisk three blocks opposite the direction of the school, and then two blocks to the right. Frisk continues to look between her and the sidewalk, probably puzzled as to where they might be going in such a hurry.

In truth, Toriel is hoping that if she arrives quickly enough, Frisk will not realize in time where she is bringing them. She fights the temptation to pick them up outright. Surely, even having lived with Toriel for a time, it would be frightening for a child to be picked up and carried away by a Boss Monster.

Toriel does not want to see what Mettaton Newscast would make of her carrying her obviously-struggling child through town once they realize where they’re going.

Speaking of, she can see the doctor’s office nearing on their right. She clutches Frisk’s hand tighter and strides with purpose.

Frisk sees where they’re obviously headed as well, and digs their heels into the walkway.

“My child,” Toriel warns.

Frisk shakes their head obstinately and continues to pull back on Toriel’s paw.

“This is for your own good,” Toriel says. “In order to grow well and avoid illness, human children must visit the doctor. They will know how to help you remain healthy as you grow older. You wish to remain healthy and grow well, do you not?”

Frist continues to struggle. Toriel uses her hold on their hand to bring them forward with her physically. This is exactly the type of public confrontation she had wished to avoid. At least it has not escalated into a true FIGHT, which would take time and could very well end in Frisk’s victory by way of stalling until the doctor’s office closes. Toriel thanks the heavens for small mercies.

Still, her child is clearly unconvinced on the idea as a whole. Frisk shakes their head violently, struggling for all they’re worth.

“Frisk,” Toriel admonishes. “There is no need to cause a scene. You must go to the doctor. I promise, I will be there the whole time. There is nothing to fear. Please, child, do not be difficult.”

Frisk opens their mouth and moves as if to speak, but nothing comes out.

“geez, tori. i heard something about a kid napping, but i think this is the wrong kinda kidnapping, yanno? where ya goin’ in such a hurry?” Sans’s voice from behind startles Toriel, and Frisk seizes the opportunity to escape her hold. Toriel barely has time to retract her claws before they’re scrambling backwards and shuffling to the side, down an alley.

Before they can get far, they’re jerked to a halt and dragged back to Toriel.

Sans returns his hand to his pocket with a lazy smile. Frisk’s SOUL remains blue, though, and they scowl as viciously as they’re able to from Toriel’s side. They mutter something, but it’s inaudible.

“come again, buddy? my ears aren’t what they once were,” Sans says, his shoulders relaxed and smile friendly as he slouches a little to be at Frisk’s level.

This is one more thing Toriel appreciates about her friend—how good he is with Frisk. Even as they frown and squirm, they are distracted from the worst of their distress. They shake their head and point at their own ears to indicate to Sans that he doesn’t have ears.

“huh? sorry, pal, i’m not catchin’ ya. can’t quite hear that,” Sans jokes. Toriel laughs despite herself at how Frisk stomps their foot and huffs.

Sans chuckles and shakes his head. “seriously, though, what gives? not sure what around here’s got you dragging your feet. ‘less you’ve got something against my crazy skills.”

Sure enough, Sans gestures to a sign caught in a sideways tornado that’s twirling itself by the roadside. One of his many jobs, no doubt. Never mind that this particular road doesn’t see enough traffic to justify having a sign-twirler, and the sign itself does not seem to advertise any local businesses.

“Frisk and I are going to visit the doctor,” Toriel tells Sans. Frisk’s struggles begin anew, and they even manage to jerk half a pace backwards at the word ‘doctor.’

Sans gently floats them off the ground and back to where they were standing.

“careful, kiddo, don’t hurt yourself,” he says. “what, you forget your apple today?”

Frisk shakes their head again, scuffing their feet uselessly against the dirt as they scrabble to move backwards. A bead of sweat appears on Sans’s skull.

“hey, buddy, you really don’t wanna do that. you can do some real damage to your soul trying to fight blue magic, and then you’ll really need a doctor. maybe take a chill pill, ok?” He looks a little concerned.

Toriel gives her friend a helpless grimace.

“I am afraid Frisk suffers from a fear of doctors,” she tells him. “They tend to disappear when I schedule an appointment in advance. Thus, we are going for a walk-in visit this afternoon, to ‘get it over with.’”

Sans glances at Frisk with a corner of sympathy in his smile. “’fraid of doctors, huh, kid? that’s tough. is it the white coats? those can be pretty intimidating.”

Frisk does not respond, choosing instead to continue scuffing their feet on the ground. Sans shrugs, unperturbed by Frisk’s nonreactive nature. “eh. you could always ask Alphys to check in on ‘em at home. she knows soul stuff. that any better?”

Frisk shakes their head no.

Toriel is reluctant to let the scientist responsible for the DETERMINATION experiments prod at her child in any capacity. She recognizes that Frisk has chosen to befriend Alphys, and that Sans vouches for her, but anyone who could use her murdered children’s SOULs as a source for scientific experimentation, no matter how good their intentions, is not someone she wants as her surviving child’s primary care physician.

Sans seems to see the source of her worries, eyes intent as his grin remains neutral. He can be quite observant, when he wants to be.

“or not, just a thought. hey, you wanna—kid, quit it.” Sans’s voice snaps from a relaxed drawl to something a touch more forceful. He interrupts himself to reach his left hand up wardingly as Frisk inches backwards despite the blue magic on their soul. There’s an ominous creaking sound. Sans breaks out in a sweat, beginning to look distressed.

“kid, seriously—frisk—”

With a sharp _snap!_ Frisk steps backwards, just half a beat before the blue magic on their soul releases them. It must hurt; their HP drops significantly, and Toriel reaches out to heal them. They don’t wince, turning around to walk back down the street at a normal pace.

Toriel hurries after them, catching their shoulder. Immediately, they squirm out of her grip and continue moving, stumbling only a little as they continue down the street to the intersection.

“Frisk. Don’t you think this is—” Toriel is nearly ready to pull them into an encounter out of sheer frustration when Frisk, moving with uncanny timing, walks into the street and disappears behind a passing truck.

Once it’s through, Toriel cannot see her child anywhere.

Sans walks out from behind the traffic light on the other side of the street, though Toriel did not see him get there, and it seems as though he would not be able to fit behind it to hide. He scouts around with troubled eyes, looking in either direction down the street.

“Do you see them?” Toriel asks, already knowing the answer. Sans shakes his head and walks back behind the pole.

“not a hair. sorry, tori. guess i shouldn’t’ve let ‘em go.” Sans arrives at her side, stepping up inexplicably from behind her. He sounds genuinely contrite, looking away as to not meet her eyes.

“No, it is not your fault. Frisk can be very…intent…about achieving their goals. I would not want them to be harmed by continuing to fight against your magic.” Toriel begins searching up and down the street, hoping that Frisk will appear from behind a building or bush. Sans walks beside her.

“yeah. determined kid.” He seems to be speaking with a flat irony, but Toriel doesn’t get the joke.

“hey, don’t worry too much. i’m sure they’ll show up sooner or later. they’re probably just gonna go visit undyne or something and wait for the doc’s office to close,” Sans says.

Toriel frowns. “I know, but…this avoidance—this has to end. It is for their own good that they visit a doctor and ensure that they are well, Sans. I cannot allow them to become ill. I will not allow it.”

Sans’s eyelights seem to waver in concern. “uh, ok…? that’s…”

She can see the exact moment that he understands. His eyelights shrink and his neutral grin turns empty.

“oh,” slips out before Sans can suppress it. He doesn’t seem to know what to say. Toriel busies herself checking in the narrow lane between two buildings—still, no Frisk.

“uh. kid’s pretty healthy. they, uh, probably won’t get sick. badly. heh. i uh, i don’t think you have to worry about them dying anytime soon. or, uh. in the foreseeable future. or unforeseeable future. pretty much all the futures.” Sans looks away. “i mean, it’s pretty cool that you care. but. i think they’d say you don’t have to worry about them. they’re not gonna, uh, leave you. it’s ok.”

Toriel appreciates her friend’s attempt, but he has clearly never lost a child.

“It is not a matter of whether…” She pauses, trying to explain herself. “I do not…thank you, Sans. I appreciate your words.”

Sans winces. “that bad, huh?”

Toriel spares him a tight smile. “I will feel better once Frisk has been to a human doctor. I have allowed them to avoid it for too long. I did not wish to force them into something that frightens them, but perhaps I should have put my foot down before now.”

If Sans has anything to say about that, he hides it behind his grin.

“well. my brother’s real good at finding humans, if you’re that worried. i bet if i call him, he could talk to them. hard to be scared with the great papyrus watching over you, and all,” he suggests.

Toriel…Toriel feels an urge she feels often.

Toriel tries every day to put aside her fear and her selfishness in order to be a proper caretaker for Frisk, but that does not mean that that selfishness does not exist.

Toriel does not _want_ to call someone else to make her child feel safe. She does not want to give up any chance she has to be Frisk’s guardian, their safety. She wants to be the person who they come to with their fears, their concerns, their happiness.

Toriel wants to be the person who can help Frisk. She does not want there to be a question of who is best equipped to coach them through a challenge—she wants that person to be her, without doubt. She wants Frisk to know that they can come to her for anything they may need, no matter what it is, and not to feel as if they can only speak to someone else. She wants Frisk to be her child _first_.

But she is trying to grow beyond these desires, because she cannot hold onto them and also hold onto Frisk. She must, as a caretaker, do what is best for her child before she does what she desperately wishes to.

Frisk must see a doctor. If they will not do so with Toriel, then she must find someone who they will trust instead.

“Perhaps…that is for the best,” she says, reluctantly, at length. “I do not think Frisk is willing to come with me…under any circumstances, apparently.”

Her heart wrenches to admit it, even to Sans, her dear friend who has known her at the height of her loneliness and never judged her for her failures. Whose inexplicable, steadfast belief in her (over jokes, of all things) had been, for a time, the only support she had.

What has she done so _wrong_ as a mother, that none of her children trust her to keep them safe? That each of them chooses to flee her, never to return, when she only wants what is best for them, to watch them grow up loved, happy, and healthy?

Some of what she’s thinking must show on her face, as Sans feels the need to pat her hand gently, looking away sheepishly.

“uh, you’re doin’ your best. i dunno what frisk’s thing with doctors is, but…it’s probably something from way before they came to us. the kid adores you. they’re probably just running ‘cause they’re scared of…you know, human stuff. it’s not…you didn’t make a mistake, or anything,” Sans tries, glancing up at her searchingly between words. “you’re, uh, you’re good. trust me, you’re exactly what that kid needs.”

Toriel weighs this, in her mind. Sans has an even head, and Toriel is not blind to the fact that Frisk trusts him with things they never tell her. They seek his advice when they are uncertain, and his company on hard nights full of nightmares. Whatever events passed Underground, Toriel may never know, but Sans and her child grew to understand each other while she wasn’t there.

They have a connection like…almost like Chara’s, with Asriel. If Asriel had been older, perhaps, and Chara not so desperately needing kindness and a gentle voice. Or…if Chara had been the monster, and Asriel the human, perhaps Asriel would have sought them out as Frisk does Sans; perhaps Chara would have played harmless pranks with magic just to watch his eyes sparkle.

Regardless, Sans and Frisk have a kinship that goes beyond humanity and monstrosity, and Toriel is glad of it. She is glad that Frisk, in their difficult position between two worlds, can feel understood.

If Frisk truly did not trust Toriel; if she were to have failed so deeply as a caretaker that they found no safety in her comfort, Sans would be the most likely to know. Would he lie to her, though, to spare her feelings?

…no, Toriel doesn’t think so. Sans knows how much Frisk means to her, and if something were truly so wrong with their relationship with her, he would let her know. At least, he would not outright deny it so staunchly. To protect someone’s feelings or for any reason, Sans can rarely be bothered to lie.

It may not be that Frisk is distrusting of her as a guardian. They’re a sweet child, reluctant to speak about their trials Underground; perhaps the fears that have caused them to vanish from before her eyes this afternoon are also something that they are afraid to speak up about, and they need time and safety in order to begin to heal. Perhaps, if Toriel were able to wait, they would come to her and tell her what is wrong.

Their refusal to be checked up on by a human healer, though; it is unfeasible in the long run. Frisk could get sick, and Toriel might not know until it became too late.

Toriel does not know what to do.

“…Please do call your brother,” she says, finally. “I shall call Frisk and see if they are willing to return. And if…if they truly cannot stand to be seen by a human doctor under any circumstances…perhaps I will consider Doctor Alphys as an option. Perhaps.”

Sans already has his phone out; it’s an improbable little thing that looks nothing like a cell phone, in Toriel’s experience.

“gotcha,” he says. “we’ll get this figured out. don’t worry about it.”

* * *

They don’t get it figured out that afternoon. Nor that evening; or even late that night. Frisk’s cell phone rings from their backpack, left alone at their home, and the human themself is nowhere to be found. No one has seen them, no one knows where they might have gone. They’re a ghost in the twilight.

At midnight, out of a lack of any better ideas, Sans repurposes an app on his phone—it’s meant to be for finding and monitoring traces of DT in normal temporal fluctuations; but it works in a limited capacity as a radar for high-DT individuals.

It’s faster than turning the whole city over, at least, if not by much. Once it occurs to him that he can just go back to the intersection Frisk ran off from, it tells him that there was a concentration of DT moving through linear time and space that walked into the middle of the street before moving very quickly down the middle of it.

They grabbed onto the truck; probably the step-up on the side opposite Sans and Toriel. Tricky, tricky. And…very painful, probably. They won’t be able to argue that they don’t need a doctor.

Sans follows the trail of DT through time. He’s gaining ground, slowly, because the kid was taking it at a leisurely stroll or maybe a pained limp once they ditched their ride; whereas Sans is also walking, but taking all available shortcuts that won’t make him lose track of them.

They got out of town pretty efficiently. Makes sense, since their best advantage was that no one thought they’d be far. To keep that advantage, they’d have to avoid the widening net of searches. Or maybe they were headed somewhere in particular. The trail goes out in straight, even lines that don’t falter for anything. Sans hopes they avoided any other traffic and looked both ways before they crossed the street.

It’s nearing dawn by the time he’s catching up; the trail is only a couple of hours old as it leads him down a badly-paved road about two hours’ hike away from the edge of town. He’s exhausted from walking and teleporting for hours; he can only imagine how the trek would feel to a panicked kid who just brute-forced their way through his blue magic. But finally, he gets a ping from the present time. About 500 feet, which is the limit on a reliable scan with his hodge-podge DT detector.

Looking forward, he can see a bus station with a bench, streetlight, and a little shelter. Looks pretty old.

Sans walks towards them at precisely the same leisurely stroll he usually adopts, keeping a close eye on his radar, but Frisk doesn’t seem to be moving anymore. Maybe they’re asleep…?

No, as he gets closer, he can see them. They’re huddled on the ground with their back to the bench, sitting curled up almost under it. Their head is up, so they’re probably awake.

Probably. Sans has heard that some humans can sleep standing up, but he’s not sure how much stock to put into the myth.

He keeps it at a casual amble as he gets nearer, but Frisk is staring straight ahead and he’s coming from their left. They don’t seem to see him. He kicks his shoes against the dry ground so they can hear him as he comes to stand next to the bench they’re under.

Frisk huddles a little farther under it. A growth spurt or so ago, they would have fit perfectly—they must have just outgrown it before they fell Underground.

Sans sits on the opposite side of the bench from them. On top, so the kid’s still got some illusion of hiding, if they need that. Sans would get claustrophobic down there, but to each their own, and all.

Silence thrives for a moment. Sans takes the time to relax and tilt his head back, but between the streetlight, the shelter, and the approaching dawn, he can’t see the stars.

Sky’s real pretty, though.

Frisk hugs their knees. They glance toward him, but don’t quite turn to meet his eye.

Sans gets comfortable.

Frisk mumbles something ending in, “…in trouble?”

Sans has half a mind to lock them in their house for a week for this little disappearing act, personally. But he’s not the one who gets to decide that. Also, they’d get out, possibly by weaponizing their hangdog expression. It’s already working on him, and he hates it.

“nah, kiddo. your mom’s real worried about you, though. she’s been looking all night.” He tries to reassure them without letting them off the hook. It’s a delicate balance.

Frisk looks back at the ground in front of them.

Sans closes his eyes and takes a couple of deep breaths, relaxing into the bench. It’s not the most comfortable thing he’s ever rested his bones on, but it’ll do.

“I don’t want to go to a doctor,” says Frisk, slowly and deliberately. Each word comes out heavy and pronounced, like they’re trying real hard to read something very important out.

“yeah,” says Sans. “i think we’re getting that.”

They seem to think for a moment, arranging the words carefully in their mind. They’ve been downright talkative lately, like Papyrus when he first figured out that he can also string words into sentences and then people will talk with him, but Sans is sensing some backwards development in that department.

“I can’t…do that,” says Frisk. “…sorry.”

Sans opens one eye and glances down at them. They’re poking at the dirt in front of them with a little stick.

He’s torn.

On one hand, this is definitely Tori’s conversation to have with them. She’s their caretaker and primary guardian, and their mother as far as anyone but the human laws are concerned. She’s the one who wants Frisk to go to a doctor—not that Sans doesn’t, in the abstract, want Frisk to be healthy; but Tori’s the one who’s their actual mother and does things like make doctor’s appointments.

On the other hand, the kid’s reluctance seems…pretty strong. And Sans kinda feels like he gets it, a bit. He doesn’t want them to be coming home terrified. He might be able to just…nudge them a little, in the right direction? Make things a little easier on everyone.

He can almost convince himself that he’s got no ulterior motives. Like not interested in getting info on—and therefore, leverage over—The Anomaly. Like he’s not a little bit obsessed with making sure Frisk _never dies_ , because when they do, the whole world is going with them. At least, this version of it.

Frisk is a good kid. They don’t deserve to be treated like a time bomb…heh. “Time” bomb. Because they can shatter any given timeli…okay, that’s enough of that.

With effort, Sans corners Scientist-Sans-who-is-trying-to-prevent-the-end-of-the-world-while-it’s-still-happening into a little room in his soul and shuts the door. He’s trying, he really is, to be actual-person-Sans-with-feelings-and-hobbies-and-a-future (not that trying means anything when he never seems to make good on it. When does ‘trying’ become an excuse for never following through? Pretty thoughts about wanting peace and love have never helped anyone; not when Sans is powerless even to change himself).

Sans has spent so long in the end of the world. He wants to be done. He wants to retire. He wants to stop watching. He wants to be alive again.

Actual-living-person-Sans likes Frisk, and is here because he’s worried about them and he gets stressed out when they disappear into moving traffic.

And he’s more likely to get an honest answer.

“any way you could tell me…why you can’t go to a checkup?” Sans asks, carefully toeing the line between wry, polite interest and friendly bemusement.

Frisk thinks for a moment. They cock their head and watch their hands as they continue to make marks in the ground. Then they shudder, and shake their head wildly. _No no no no no._

Actual-person Sans is definitely justified in wanting to know what the root of the issue is, right? That’s a concerning action. He can be curious.

But is he curious because he’s concerned?

…yeah. Yeah, actually, he’s pretty sure he is. He doesn’t like the idea of something this upsetting lingering under the surface for Frisk, and it’s an even split between searing panic at the thought that they’ll dissolve this timeline over it and genuine compassion for a scared, stressed kid. An even split is pretty good.

“ok,” says Sans. “you don’t gotta tell me anything. but, you know you can’t always run away from this stuff, right?”

Frisk continues to shake their head.

“uh, no, you can’t run away forever, or no, you don’t know that?”

“I can’t,” Frisk says. “I can’t go to a doctor. I don’t need one. I won’t get sick. I’m not hurt. I won’t. I can’t.”

Sans whistles a breath out through his nasal cavity.

“…you know tori’s not gonna take that for an answer, bud,” he coaxes. “she wants you to be safe and live a long, healthy human life.”

Toriel is amazing—she’s someone Sans really does admire. She’s seen so many humans come and go, and Sans is dead certain that she’s shown the same warm heart and genuine compassion to each of them. It’s not her fault none of her kids knew a good thing when they saw it. Sans is just sorry that she’s been left alone so many times. It isn’t right for such a nice lady to hurt like that.

So, not that it’s a big deal or anything, but Sans would do pretty much anything for her. He figures anything she would realistically ask of him would probably be the right thing to do, anyway.

“i don’t really get how, but apparently you gotta have doctors to stay healthy. you know how many things can go wrong with a human body?”

Frisk thinks for a moment and shrugs sullenly; jerking their shoulders.

“me neither. i didn’t bother to look. but probably a lot,” Sans says. “you have all that water and gooey stuff inside. what if you get dried out and evaporate?”

Frisk pauses in their stick drawing to look at him blankly.

“food for thought. i’ll give you that one for free,” he says.

Frisk twitches their face like they might think about smiling in another life. They lay their head on their knees.

Sans has actually looked into what can go wrong with a human. He has looked extensively into human research on that very subject. He wouldn’t call himself an expert, but he knows enough to know that some things need to be checked on, especially in kids. And that vaccines are important. Humans can get really sick, and sick humans can get really gross.

He’s not sure he could tell if something were actually wrong, though—he just doesn’t have the data record he needs.

Theory is great, Sans loves theory, but how does he know sick-pale from hasn’t-seen-the-sun-in-a-while pale from scared-pale? What’s the difference between a human who isn’t sweating because they’re not hot and one who isn’t sweating because they’re too dehydrated and they’re gonna die? Sans doesn’t have skin. He doesn’t know. He can get a read on their SOUL, but once a physical ailment has shown up in their metaphysical essence, it’s probably too late. What’s he supposed to do, rely on instinct?

Yeah, he’s on team ‘get the kid checked up on.’ Doesn’t have to be a doctor, but at least getting their measurements and vitals down somewhere and comparing them to an experimental average will let them know if something’s terribly wrong. There’s a gazillion humans running around going to doctors. There’s gotta be enough data out there for an average.

Sans lets the kid settle for a bit, watching the sky get lighter as he mulls it over, prodding at the problem to see if anything’ll slot into place. The sun always comes up faster than he thinks it will—twenty-four whole hours to move across the sky and back again, but it take no time at all to cross the horizon.

“seriously, though,” Sans says, once the sun is more than halfway up and he’s judged that enough time has passed. “you can’t do this every time. you know that, right?”

Frisk curls in tighter.

“Then,” they start, “then, I gotta go. Can’t. I can’t see a doctor. ‘m _sorry_.”

Sans sits up a little straighter despite himself, turning directly to face the miserable puddle of human to his right.

“frisk,” he says.

Frisk makes a jagged sound.

“’m _sorry_ ,” they say again, their rough voice dragging out of them harder than old, heavy chains.

Are they serious? Would they rather just…up and leave, than see a human doctor? Cut ties with a perfectly happy life to avoid a half hour of unpleasantness?

Then again, it wouldn’t be the first time. From what Sans can tell, they’ve made no attempt to contact any human family or friends; they left the Ruins when they could have lived happily there; who’s to say how many timelines they’ve abandoned already…

Is that what they’re talking about? If they can’t avoid a trip to a human doctor, would they time travel to get out of it? Have they already?

“Not,” Frisk grits out, “not gonna…put everyone back. Make anyone worry. Just. I. I don’t know what to do. So. Can’t be here. Gotta go.”

And be the eighth kid in a row to run off and die on Tori. This time it might actually break her heart. Not to mention what it would do to the rest of them. Papyrus would miss them, too, for one.

“…i think you’re missing a couple steps there, buddy,” says Sans.

Frisk huffs a breath out hard.

“so. you can’t go to a human doctor. and you can’t say why.”

He doesn’t push for more information. Their shoulders relax a fraction.

“tori wants to make sure you’re gonna grow up to be a healthy frisk.”

They bury their head back in their knees. The sound that comes out of them is complex, but Sans is going to focus on the bright side and call it ‘frustrated,’ rather than something like ‘grieving’ or ‘defeated.’

“what, no good?”

 _Is_ Frisk healthy? Would they say anything if they weren’t? Probably not. Would they let Sans put it together himself? Well, they can’t really stop him. Except that they can if he wants to know anything specific, because he needs tools to check on them. Sans is observant, but he can’t clock pulse, weight, and temperature without some sort of measure. And listening to their breathing would be kinda creepy.

And, you know, they could repeatedly unwind time every time he gets a hint of a right idea, forcing him to forget over and over, killing the him that knows anything at all to start over with a smiling clean slate who trusts them and doesn’t even know anything is wrong. Because Sans really does trust them, or he’s trying to, so hard that they could absolutely screw him over a hundred ways without even noticing. Without caring. Or they could wander off and run out of DETERMINATION and die where he could never, ever find them. They could just be _gone_.

No. _No_. Sans is _choosing_ trust and he’s choosing it whether it’s a bad idea or not. He _trusts_ Frisk. He already loves them like they’re his own family; he’s going to trust them like it, too. They’re going to live. The timeline will survive. He cares about them. He wants them to be healthy. He has no reason to be panicking like this.

He’s their concerned friend right now. And forever. That’s all he is. That’s all he’s going to be.

Okay. What can he do with this…? Changing Frisk’s mind is a non-starter; they have too much DETERMINATION for Sans to really have a good shot at success, and he doesn’t know what the problem he’d be arguing against actually is. Changing Toriel’s mind would be temporary at best and ultimately counterproductive. Lying his proverbial pants off…

Huh.

Lying his pants off it is.

“ok. how about this?” Frisk trusts him enough that they at least unbury their head from their knees and look at him. Their eyes aren’t red or anything—well, no redder than usual—so they’re probably doing fine.

“if you’re really against going to a human doctor, there’s gotta be a good reason. i trust you. you don’t have to tell me if you don’t want to,” he says. That much is true, at least. He trusts that Frisk has a reason for the things that they do. “i can talk to your mom, try to convince her you don’t need to go.”

Frisk cocks their head, but they’re listening.

“yeah, don’t expect me to do this again, kiddo. this is a lot of effort for one day…uh. two days, i guess.” He nods to the sun, just touching the horizon. He probably should have texted someone that he found Frisk.

Frisk looks directly into the sun, like they like to. It is a pretty cool concept, a star so near that it can warm the whole planet. Weirdly, Sans always gets an instinct to shield their eyes when they look at it, like it’ll somehow hurt them if they make eye contact.

Sans’s instincts with humans are pretty wonky. This is why he needs facts and research—obviously going off intuition is just gonna make him do weird stuff for no reason, and then he’ll get distracted from what’s _actually_ wrong.

“so—if i do this, you gotta do me a favor, too,” Sans says. Frisk looks back to him, unblinking.

Here’s the gamble.

“come to alph’s with me tomorrow. uh. today. she’s got a whizgig she made that can look at a thing and tell if it has DETERMINATION or not. we both know you do—it won’t tell us anything we can’t see from a basic encounter—but it’ll make me feel better. not, uh, not like the physical stuff really matters, for you, anyway, huh?”

Normally he wouldn’t tip his hand like this, directly implying that Frisk is a time-traveler and can simply go back and avoid any physical ailment before it sets in; but they know he knows.

Or, they know he’s potentially capable of knowing, if he’s read them right. They’ve made some pretty direct allusions to their powers themself where Sans is concerned. And it gives him the perfect excuse to be negligent in actually getting them to a human professional—why bother with that when they can just unwind their own death?

Well, unless he is to actually care about the survival of his timeline; which he does, being as he lives in it, and all. He would really rather Frisk not die in the first place. Like, really _really_ rather. Dead humans are weird and upsetting and he doesn’t want to deal with it.

But the person who holds the world on tape and gets to record over anything they don’t like probably has a different perspective on that sort of thing.

Hopefully, between their relative immortality as a reasonable excuse to not care about seeing a human doctor, and the surprise of having Sans go out on a limb for them, they won’t think too carefully about what tools exactly he wants to poke at them with. Or realize that he could have just measured a yes/no for their DT with an app on his phone, and is in fact doing that right now, if that’s what he really wanted.

The fact of the matter is, human bodies can screw up in all kinds of ways that monsters would be helpless to repair. Left to his own devices, all Sans can do is follow the contradictory urge to cover them in a blanket and put ice over their eyes and on anything else that hurts, which doesn’t make sense because he would freeze their eyeballs, or something.

And he can make them drink milk. Strong bones are the most important.

But those things won’t actually keep them healthy, or fix them if something’s wrong. So the kid needs to get checked over somehow. If they can’t go to a real human doctor for real humans, the next risky option is for Sans to cross his fingers and stake their health and his timeline on half-understood research that he’s mostly making up on the fly.

That is what he got his degree in, so this should be totally fine.

As long as they don’t really understand what he is and isn’t capable of measuring in the lab, he can probably get them to sit through a couple of different tests—thermal scan to make sure their internal temperature’s fine; magical scan to see if living with monsters has done anything weird to them or maybe even made them sturdier; finally check their DT levels to see exactly how much of it they have; maybe an x-ray to look for any underlying conditions…?

Height’s a good one, too. Better nutrition means taller humans, so he’ll at least know if they’re eating alright. He’s a little nervous about how they never eat human food.

It’s not ideal. He’s really rather have someone who knows literally anything about human medicine check them out and give a 100% guarantee that they’re absolutely not going to die. But this is the best compromise he can think of besides tricking them into a real, human medical doctor’s place and leaving them there. Which wouldn’t even work, probably; they’ve already proven that they’re willing to hurt themself to escape.

Not to mention how tricking them like that would shatter their trust in him entirely, and Sans…really doesn’t want to see the look on their face when they realize he tricked them into something that scares them so badly.

But Toriel is really worried, and she knows more about human children than anyone. And Frisk’s already as good as said that there’s something wrong, something that could be hurting them and is definitely scaring them and making them think about doing weird stuff like run away to climb some other mountain and die in a hole where Sans won’t be able to find them until they’ve starved and rotted to dust. He can’t just let that lie.

Sans’s intentions are good. Whatever Frisk is scared of with human doctors, Sans won’t do it to them. He wouldn’t hurt them. Not even if it killed him (because what does dying a little sooner mean when every Sans before him has been erased, when statistically speaking he will be destroyed and forgotten too, no memory left of the progress he made and the person he became) (because the person he’s become loves them too much to hurt them, ever) (because monsters are strange).

Frisk can be afraid of doctors, but they don’t have to be afraid of _him_.

“Just checking that I’m DETERMINED?” Frisk asks. They’re still looking at the sun with intense concentration.

“yep. you’ll need to stand there for a few minutes and Al might need to poke you a few times, then something’ll ding and we’ll know you’re good to go. you, uh, you’re not scared of needles, right?” Sans asks. There are tests humans can do on blood to make sure they’re doing okay and that they have all the stuff they need inside of them in the right quantities, which would go a long way towards making Sans feel better.

Frisk grimaces. “…I have to?”

Sans evaluates them. They seem like they’ll probably still agree.

“yeah. sorry, bud, part of the process. i can ask paps to come if you want someone to be there with you,” he offers. It would be a bit harder to hide that he’s taking more than one test from Papyrus, who knows how monster technology works and is absolutely willing to call Sans out on his shit, but he’ll do what he’s gotta. And if maybe he kinda hopes someone stops him, if he feels maybe a little bit bad for lying, blatantly, to a child who trusts him, so he can get scientific readings off of them without their consent…

Oof. Maybe he should think of it more as…benevolent misdirection. He’s doing it for the right reasons, isn’t he? It’s not like he’s gonna hurt them, or anything. He’s just…compromising ~~his integrity~~. Helping them avoid their fears while still making sure they’re healthy. He needs to be sure they’re alright. This way he can help Toriel _and_ Frisk.

Thankfully, Frisk declines. “Just Alphys. No one else.”

Whew. Sans didn’t even think about the possibility that Alphys wouldn’t be there. “sure, kid, whatever makes you comfortable. it’s no skin off my back.”

Frisk frowns at the sun before looking down at their stick-sketch in the dirt. They make some more lines.

They seem awful stiff. Maybe they aren’t ready to go back quite yet.

“welp. i’ve been awake for too long. you let me know when you’re ready to head back and we’ll take a shortcut,” Sans says, leaning casually over to lie across the bus bench. Frisk hums to acknowledge him and keeps digging with their stick. Seems like they’re tracing over the same lines, deeper and deeper.

It’s a sketch of a little heart shape, with jagged gouges breaking it to bits.

Sans looks at the sky, instead.

* * *

As it turns out, Sans doesn’t need to convince Toriel of any part of his half-baked plan to use Alphys’s stuff to check Frisk out himself. By the time Frisk wakes him up and he’s done bringing them home, Alphys herself approaches him.

“S-uh, Sans!” she calls, before he can go home to start catching up on lost sleep. She looks pretty worn, herself—everyone was up all night trying to find where Frisk may have gone. He definitely should have texted that he found them.

“‘sup?”

“Could you, uh, c-come to the lab with me…? There was, Queen Toriel asked me to, um, look at? Frisk? To make sure they’re, healthy? And I don’t know? What I’m doing????” Alphys stutters, glancing around and at anything but Sans.

Huh. That was a quick turnaround. But then again, this is the only solution Sans can see working at all. They can’t have the kid running into traffic every time they need a check-up.

“sure,” Sans says. “follow me.”

Alphys sighs, but follows him into the nearest door—Toriel’s coat closet, incidentally. Not that it leads there when they enter it. In a moment, Alphys is blinking into the light of the lab while Sans makes himself comfortable sitting sideways on her rolly chair. The arm fits right under his knees if he scrunches up a bit.

“Please pretend to take this s-seriously,” Alphys sighs.

Sans begins spinning himself against her desk with his feet. “i’m plenty serious.”

“Sans. I really don’t know w-what to do. The, the _Queen_ asked me to do something really, really important, but—but I don’t know an-nything about humans, who are, alive? I’ve only ever—I j-just know SOULs, and dead humans, and, that isn’t—doesn’t really t-tell me what I need to know, for this,” Alphys frets. Sans can see her twiddling her claws into her sleeves in between rotations.

“yeah,” Sans says. Her expertise is in SOUL science, most recently, and before that she was best at magitech. Luckily, that’s exactly what he needs.

Well, a biologist might be nice, but there haven’t been monster biologists in…ever, maybe. Not much to study when you’re made of dust and magic.

“Sans!”

Alphys grabs an arm of his appropriated rolly chair. He glances down at her. “yeah?”

Oh. That’s a sour expression. Maybe he should be a little nicer. He should definitely be a little nicer.

At least Alphys is used to Sans being Sans at this point. He has the dubious honor of being just about the only monster she feels confident chewing out when he gets on her nerves; she has the dubious honor of being just about the only monster he’d never judge, not for anything. Maybe he should have, with the Amalgamate mess, with the lying to Asgore about Mettaton being an artificially-created SOUL, with the self-destructive spirals, but—nope. They know each other too well.

Thus, Alphys feels totally confident snagging the arm of his rolly chair, leaning in, and reaming him out. Pretty politely, all things considered.

“Sans, I need your help, I don’t need you to steal my lab chairs and stare at the ceiling!” she says.

“this is my help,” he jokes. She doesn’t seem to appreciate it, so he shifts to at least be sitting in the right direction on the chair. “ok, seriously, though. what are you thinking you’ll do?”

“I d-don’t _know_!” Alphys says. “I don’t know what I’m doing! I just! Didn’t want! To say no! To the Queen!”

“feel like she’s more of an ex-queen now…i don’t think she’s really thinking of gettin’ back with asgore any time soon.”

Sans may be avoiding the issue, a little bit. He’s a little conflicted, alright? But Alphys’s look says she’s not gonna be taking much more of his conversational twistyloops today.

“ok. helping. she asked you to check up on frisk, right? get a head start on if they’re healthy, what they need, that kind of thing? anything she’ll need to keep in mind in the future?” he asks.

Alphys nods firmly, letting go of his armrest. She shuffles through some papers on her desk.

“I have some equipment already, f-from the DETERMINATION experiments. That might help. But I, I really don’t know what humans…need? Or, what to look for? Or what can go wrong? I need a human expert,” she says. Eventually she unearths a pastel pink notebook, and begins flipping to find an open page.

“what’re you asking me for?” Sans can’t help but wonder. Honestly, he’d kinda figured he was here as a sounding board and maybe moral support. For whatever moral support Sans can provide.

Alphys pins him with an unimpressed look.

“W-well, my human reference book went missing from my l-lab about when Frisk was going through Snowdin,” she says. “All of the human reference books. You know, from th-the private lab, which no one can get into. Except you, or me. A-and it would be really hard to sneak all those books past me unless you had some sort of shortcut.”

Sans has half a mind to razz her some more, but he doesn’t actually want to move her to violence. He shrugs. “guilty.”

She doesn’t bother getting upset with him for appearing in her lab at will, for stealing her books or her rolly chair or leaving bags of dog food (and ‘dogs, which are food but not dog food, unless Papyrus cuts them up and puts them in dog food, in which case they are dog ‘dogs) lying around. Sans used to live there, too. Those might’ve been his books in the first place, or belong to someone long forgotten.

“So what did you learn?” she asks instead.

Hmm. What did he learn?

“uh. humans do have real, whole skeletons in them,” he starts, because that was the weirdest part. He felt kind of gross and had to put down the book for a bit after reading that. Imagining himself surrounded by squishy, wet, perpetually rotting and regenerating flesh was…he kind of wanted to sandpaper his bones after that just to feel clean. “they use them to make blood. super weird. also, humans are kind of gross.”

She probably wants something a bit more helpful than that.

“they’re supposed to have a pretty specific temperature range—too much and their brains’ll cook, too little and they’ll freeze. Ambient temperatures they can take, but their internal temperature has to stick.”

What else…?

“they need to have enough water in them or they’ll die. they need to have enough food or, again, die. if they don’t get enough different kinds of food they won’t necessarily die, but they’ll be pretty bad off. some of them need help digesting sugar in their food or, again, the dying,” he lists. “sugar is bad for them but they also need it to live? that part kinda confused me. they need it in their blood for sure, though. seems kinda gritty.”

That about covers temperature and diet, which made up a whole chapter of the reference book Sans liked best. It was meant for first-time parents, but hey, whatever works. It was the only one that really told him anything about kids.

“as far as i can tell, the best way to tell something is wrong with a human is if they sleep more than, say, 12 hours a day. that probably means their body is shutting stuff off to try to keep them alive. good news for us, ‘cause i’ve never seen frisk sleep at all,” he says. Alphys takes rapid notes, sketching out blanks to fill and tests to run.

“So, thermal scan for internal temperature, density scan to make sure they have enough water…what can we do about food? What happens if they’re not getting the right kinds?” she asks.

Good old Alphys; she can really get things done in a pinch. Which means Sans can pass off most of the legwork to her, probably.

“got that one covered. there’s a bunch of tests humans can do to their blood that’ll tell you if they have stuff wrong with their, potassium, or hormones, or somethin’. you can just send ‘em any old blood, no questions asked, and get a bunch of stuff looked at. pretty neat, huh? i got frisk to agree to let us stick ‘em,” he says. “you _will_ need to look up how to store blood. i think it needs to be cold? human blood really doesn’t want to be outside of its human.”

“Right,” Alphys mutters, jotting that down. “How about sickness? How can we tell if they’re sick or hurt?”

Sans shrugs. “ask? there’s a lot of ways humans can get sick—human sickness is actually little tiny creatures invading their body and hijacking their cells, and there’s all sorts of different types.”

Alphys gives him a look. “Now you’re messing with me.”

“really wish i were, alph,” he says. “think you’re just gonna have to tell tori that humans get sick sometimes, and there’s not much you can do about it. it’s usually nonlethal, just puts ‘em down for a week or so. they need more water when they’re sick.”

Alphys scratches something down, grimacing. “I’ll look into that more later.”

“oh. right. there’s some stuff you can give them that stops them from getting certain kinds of sick. we probably need to know if frisk’s gotten any of those before, ‘cause it seems like vaccines have to go on a schedule,” he says. “tori might feel better about that, at least.”

“Okay,” Alphys says, appeased. “That’s good. We can ask Frisk if they’ve gotten that stuff done before, and I’ll look up what the schedule is. Can you sneak into somewhere and get some of whatever we need for vaccines, or is there an order form we can fill out somewhere?”

First resort is thievery, second is asking nice. Alphys’s moral boundaries have been known to blur in the face of science. Not that Sans is on any higher ground, since he’s definitely gonna commit a stealing for at least some of this equipment.

As for how to get it legally…

“no idea. i always figured i’d never have to worry about it, either way.” Because Frisk would cross the Barrier back to humanity or die Underground and collapse the timeline, probably way before any disease could get them. It hadn’t been his most immediate concern.

“Right. So, get some blood, thermal and density scans, look up more stuff on humans and illness. Can humans get hurt without damaging their HP?” Alphys’s page fills and she moves on to the next one.

This is one that Sans hasn’t got the answer to.

“uh, humans don’t know about hp,” he says. Before Alphys can accuse him of yanking her chain, he adds, “no, seriously. they didn’t have anything about souls in the book. no hp graphs, no magic, no nothing. nada on DT, either, but i’m thinkin’ there might be a connection with blood somehow. you know, red liquids, naturally produced, they get lethargic and weak without them, they need them to live. humans’re totally clueless about that stuff, though—i don’t even know what a human’s hp should be.”

“Great,” Alphys mutters. “And we only have three reference points, which vary from single digits to nearly 700. So basically nothing.”

Sans didn’t know anyone took notes on any of the previous humans’ HP levels—he’s never seen that written anywhere, anyway. Then again, he’s pretty much avoided biology. It’s gross and there’s no real use for it without humans around.

Physics is his wheelhouse, and that covers more than enough to keep him busy. He branches into engineering and magical constructs when he’s feeling ambitious.

Learning now that the previous humans had such an array of stats, though…700 HP? That’s…a lot. Even Papyrus is only at 680, and his HP is higher than anyone’s in their half of the Underground, except for Undyne, whose 1500 HP is ridiculous and frankly unnecessary.

Sans is…pretty glad he didn’t cross paths with any of the previous humans. He can bring his all to combat if he needs to, but 700 HP? And, assuming Frisk’s 20 is the default, the amount of LOVE the other human would have to have to boost their stats that much? He would probably be very dead.

“Okay,” says Alphys. “Alright. For now, we’ll err on the side of caution and assume that my theory is correct, and due to their physical bodies, humans can receive damage that isn’t reflected in their HP. How do we look for that?”

Sans has no idea. He’d never thought of that. “uh. maybe it’ll hurt?”

“You really think so? Without losing any HP?”

Fair point. “…let’s add that to the ‘look up later’ list. they’ll bleed, i know, but also sometimes they don’t if their skin isn’t broken? apparently they can get hurt without breaking their skin and they’ll swell up and change color, but, uh. honestly, i didn’t really notice a difference in the picture. i got the color thing, sort of.”

Relative thickness of human limbs is not something Sans is familiar with. He’s relatively confident that he would notice if Frisk changed shape, probably. Maybe.

‘Bruises’ and ‘contusions’ might have to be part of Humans for Dummies 201. Maybe 301.

Speaking of changing shape, though, “oh, right. they’re supposed to be at a certain height and weight for every age. there’s charts.”

Alphys notes that down.

“Alright. Adding in height, weight, looking for any weird colors or swelling, we’ll check their stats just in case…”

“DT,” says Sans. “i want to get a real close look at their DETERMINATION levels. if we can do any kind of trait-imaging on their soul, that’d be great.”

“Their DETERMINATION…?” Alphys asks. “I thought you said humans didn’t know about…oh. This is for you?”

That’s probably the most delicate way to put ‘is this to put your mind at ease because last time we were extrapolating about high levels of DETERMINATION and what they could do you had a breakdown, abandoned all of the things you love—’ (except Papyrus, who his bags packed fifteen minutes after Sans staggered home, and staunchly refused to be abandoned)— ‘and moved out to the middle of nowhere, and I had to stalk your shitty joke blog every day for a month to make sure you hadn’t Fallen Down?’

At least, Sans is…pretty sure DT studies are what caused that? Or, he was upset because he missed something important…? Somehow, it never sits quite right in his…

What was he thinking about?

Oh. DETERMINATION. It freaks him out. Right.

“let’s say i’ve got a pretty strong hunch,” says Sans. “just wanna get some numbers on it.” _so i know how terrified to be._ “it’ll probably help as part of a general checkup. humans need DT to live.” _every day i am terrified that my whole life will disappear and the next version of me won’t even remember that he’s missing it._

Sans isn’t some kind of nerd, so he doesn’t give voice to any of the subtext. Alphys is a sharp cookie and doesn’t buy his blank look and disinterested slouch, but she shows mercy and doesn’t force him to admit that he feels visceral fear of the natural abilities of a goddamned child.

Frisk is a good kid. Sweet. He loves them with his whole heart. Tori trusts him to protect them, if it ever came down to it. And he will. Has. Does. Whatever.

The little room he keeps shoving Scientist-Sans-who-is-trying-to-prevent-the-end-of-the-world into is empty and its proverbial door is swinging off the hinges. Sans walks himself back in and nails it shut this time. He chose to love this goddamned kid despite everything, and he’s going to do it right.

With effort, Sans drags actual-person Sans up from where he happened to be drowning, shakes him off, and tells himself to get a grip.

“anyway. i’ll leave you to the nerd stuff. i’ll grab some of the little blood jars while i’m out, see about how to keep it from getting all gross and congealed. think the kid needs someone to bring them lunch anyway, so.” Sans works in the cafeteria of Frisk’s school sometimes. Schools still won’t serve monster food, and Frisk won’t eat anything else, so Sans sneaks it in and cuts little cat ears into the hotdogs to make them smile. It’s not a big deal. “i’ll, uh, text you some links. don’t go on webmd. seeya.”

This is where Sans would tell a distracting joke and get his conversational partner to laugh, then leave with appropriate comedic timing in a weird and nonsensical way. But it’s just Alphys, so he doesn’t. She gets it. She lets Sans get away with abruptly sneaking out of a conversation that veers too close to DETERMINATION, same as he does for her. Except he’s a better liar, so he sometimes covers for her, he guesses. Friendship is pretty neat.

Alphys is giving him that look of mixed comprehension and incomprehension— _I understand why you’re upset but I don’t understand at all_ , because she knows but she doesn’t _know_. She can’t possibly understand, because if she did, she would be just as terrified as Sans is. She just looks at him with the weight of all their secrets and a little pity, and in the end, she doesn’t say anything.

For all their similarities, Alphys isn’t trying to kill a part of herself just to try to exist in the present timeline.

Sans sticks a couple more nails in the imaginary door and puts up a sign.

_don’t dead  
open inside_

Like that edgy TV show with the gore and the evil rotting undead humans who ate that horse. Sans hated that show—the rotting flesh; the awkward walk; the pathetic, half-destroyed human bodies still dragging themselves mindlessly on. The way the ‘zombies’ were basically cannibals who got nothing but a shot in the head.

So maybe he’ll leave the imaginary door alone now. Maybe Scientist-Sans will just curl up and go to sleep so he doesn’t have to touch the reference. Maybe everything will go just swimmingly.

Sans shuffles off and Alphys lets him go. Small mercies.

He’ll get it together before he goes to see the kid.

* * *

Alphys is having second thoughts about bringing Sans in on this.

It was just instinct—she had a problem, she knew he’d done obsessive research in the area because when is Sans’s research not obsessive, she had a time limit she couldn’t possibly meet without consulting someone with experience in the field. As far as monster scientists go, it’s just Alphys and Sans now (someone must have taught them, right? But she gets migraines and Sans forgets whole conversations if she talks about it, so she doesn’t).

It was natural to bring him in as a consult on human health, if nothing else. He literally has the book on it. And he’s always helped her before, where he can.

He’s a pretty lackadaisical guy these days, is Sans, but he’s always been there when she needed him.

And he’s here for her now, too! The issue isn’t that he doesn’t know what he’s doing, or that it’s not helpful to have him in on it—he’s almost suspiciously well-prepared for a spontaneous doctor’s exam, and Alphys will eat her foot if he didn’t take those books with the same idea in mind, of knowing what to look for before anything goes wrong.

Sans loves Frisk like he loves Papyrus, and Sans’s idea of love is knowing everything about someone. Even Alphys can’t count all the times he’s appeared benignly in the background of her life, not really there to chat but just to be present and aware of her and show passing interest in what she’s doing. It’s a little weird, but Papyrus can walk through walls and waits for 10-hour stints outside of Undyne’s house just to hang out, so Alphys is pretty sure skeletons are just like that. Maybe it’s the undead-type monster connection, but all of the skeleton brothers’ friends have been lovingly haunted since day one.

Since before day one, in Frisk’s case. Alphys hasn’t asked if he somehow knew they were coming or what, but Sans showed up in the lab to tell her he wouldn’t be lifting a finger to harm any human that came through the Underground, ever, a couple of months before Frisk fell.

It was a complete turnaround from his previous suspiciously passionate belief that humans don’t belong in the Underground under any circumstances, and should probably be thrown into lava just in case. Or cremated. Or cut in half, or vaporized, or otherwise destroyed completely, preferably on a molecular level.

Sans doesn’t know any more than any other monster about humans or being human, but he knows a thing or two about the insides of seven little coffins beneath the palace. He knows enough that he checks in on them once a week.

He’s only ever found someone moving once; and that once, Sans brought his find home and named him Papyrus. He was sitting outside Undyne’s door within a month, wanting to join the Royal Guard without a hint of irony.

So it might have been a little cruel to ask Sans to learn all about how to keep a living human healthy, information which will never help him or Papyrus. It might be kind of grotesque.

To be fair, she isn’t sure Sans is even aware of how skeletons come into existence—you’d think he’d have it figured out by the time Papyrus was around, but he seems to conveniently forget his weekly visits below the palace. Or at least, he never talks about them, even though she’s literally been there with him before.

She’s tried talking with Sans about what he can remember, but all he’ll say is that he comes from “around,” that Papyrus is absolutely 100% definitely his brother, and when pressed, that he thinks they might have grown up separately for a little while in two Underground cities that must not exist anymore, called Boston and Detroit. Which no Underground city has ever been called, because they’re all named with puns based off of landscape, and Sans knows this.

He just seems to genuinely not notice the contradiction, or that his eyes drift towards America’s upper east coast even when they’re talking about other continents on the map. Or that the concept of Frisk, or any other hypothetical fallen human, being killed sends him headlong into fight-or-flight. Which is a reactive state that non-skeleton monsters don’t even have.

It’s possible that Sans is afraid of the implications of Frisk’s high DETERMINATION. Alphys believes that he is. He has a very human fear of death, and erased timelines aren’t so different from that.

It’s just that she thinks that that’s not all he’s afraid of. And she’s not sure how to tell him that what he’s desperate (DETERMINED) to prevent has already happened; a long, long time ago.

Or maybe he’s not afraid of the fallen humans’ eventual fates, so much.

Sans wouldn’t mind another skeleton monster around—his one and only stipulation when he and Papyrus moved to the Surface was that they added a room to their house, just in case anyone needed a place to stay for a bit. Probably to avoid the awkward roommate-shuffle he had when Papyrus first came into being and had to share Sans’s barely-functional studio apartment in Hotland while Sans slept in the lab half the time just to give him the illusion of having his own space.

No, what Sans is afraid of is the risk in the process, Alphys is pretty sure. The concept that Frisk may die somewhere where he can’t find them terrifies him. Even while he followed them pretty much everywhere Underground, he checked in to make sure Alphys had eyes on them, too. He was just about unreachable for a while, alternating between watching them like a hawk and refusing to witness any of their battles.

Sans is petrified of losing track of them, of getting distracted, of finding another coffin with scratch marks on the inside and a little pile of dust, where his would-be sibling starved and died all over again before he could find them. And with the whole Surface open to him, he and Papyrus could disappear a lot farther than Snowdin.

But all he’ll say is that he has to stay involved if he wants to make sure the timeline is safe. He just needs to keep an eye on the one creature capable of ruining everything.

Sure. Because showing up to Frisk’s PTA meetings is really about protecting the timeline.

And now, this. Sans is helping Alphys out with a mock-up exam to make sure Frisk is ‘healthy,’ already a dubious term, which of course he is going to take as a test that will end with Frisk alive or dead. And Alphys is not totally sure it was a good idea to even let him know it was happening.

Sans’s gut feelings (haha. Thank you, Sans, for ruining Alphys’s sense of humor) are dubious for most monsters, but helpful when it comes to humans; combined with his research into what human doctors have discovered about health, he’s an asset, definitely. Plus, he and Papyrus have never struggled with getting in and out of anywhere they want to go, so he’s really handy to have on her side for getting specialized vials and any human-specific equipment that she doesn’t technically have totally legal access to right now. All of that is great!

But. There is the little downside of how frankly manic Sans looks when things like DETERMINATION come up, or human remains, or humans sustaining themselves after death.

Also alternate timelines, endangerment and death of the eight fallen humans, or the possibility that Frisk might die in any place that isn’t right in front of him where he can see them. Or the further possibility that Frisk will die and the timeline will dissolve before he can get to their body.

Or, as a general statement, the possibility that Frisk may disappear and/or die. Or that Papyrus could possibly one day go somewhere far away and get lost and starve to death, or…

Alphys isn’t really sure what Sans remembers or wants to remember, but it’s enough that he should maybe not be interacting very much with the idea that humans are at risk of dying. Specifically, the fallen humans; he doesn’t seem to care that much about humanity in general. Alphys has hypothesized that there’s something about humans living near (or being killed by?) monsters that makes the occasional skeleton monster sprout up, and Sans seems to somehow know that other humans aren’t a concern for him personally. Or he just doesn’t care about most humans, potential skeleton monsters or no.

Frisk is very much Sans’s concern, though. They’re a fallen child and a personal friend, and also Papyrus’s friend, which makes them doubly important in Sans’s weird world hierarchy. Alphys isn’t sure what he’ll do if they turn out not to have a clean bill of health. Sans is refusing to consider the possibility, as far as she can tell. And that would be fine, if Alphys thought they would come up with good results! Well, it would still be kind of bad, but…

Alphys has her own suspicions. About how Frisk’s skin is always cold, almost certainly out of the narrow range of temperatures Sans gave her. About how they haven’t grown at all since falling Underground. About how they never even seem to notice the difference between Hotland and Snowdin, much like how Sans and Papyrus can stroll from one to the other without a shiver. A million other little things, half of which Sans himself has told her before convincing himself that he just doesn’t know how humans work.

Maybe she’s wrong! It’s totally crazy to think that Frisk is a monster just because they don’t really act human all of the time. They live with monsters; of course they’ve picked up a thing or two! So Alphys is definitely gonna do the exam as well as she can! And hopefully report to the Queen, who already doesn’t like her and doesn’t trust her because of Alphys’s dubious history of human experimentation, that everything is a-okay!

But. Maybe she’s right. And if that’s true…Alphys doesn’t know what she’s gonna do.

* * *

 _Alright_ , Frisk thinks. _Okay. It’s OK. It’s just Sans and Alphys._

Frisk convinces their stupid dead legs to move a little faster on the last few paces to the front door of Alphys’s lab. If they were alive they would be sweating. If they were alive they wouldn’t need to be doing this at all.

How can they tell Toriel that they’re never gonna grow up into a strong, healthy human? How can they possibly explain, when even Frisk doesn’t know how they’re still alive?

Frisk climbed Mt. Ebott, and fell a long, long way, and landed with a sickening crack. It was just their luck that they landed on the grave of someone who also wasn’t ready to die yet. It was just their luck that there was something about their SOUL, or DETERMINATION, or Chara, or even Asriel that let them crack their spine back into place and shuffle to their feet, their cooling body still under their tenuous control as long as they used all of their concentration on it.

Maybe it was that Chara’s SOUL was absorbed by a Boss Monster, and so Frisk could absorb their SOUL like they were a Boss Monster, too. Maybe it was that Frisk refused to die, and Chara was just there as a coincidence. Maybe it was magic. But Frisk’s heart hasn’t beat since they hit the ground, and they’re still moving. Their SOUL is as strong as ever.

But what if their DETERMINATION runs out? What if someone notices that they aren’t growing up? Are they gonna rot while they’re still alive, and then be a skeleton? Or will they just turn to dust?

Frisk is dead, but…they don’t want to die.

So…Frisk is gonna tell Sans and Alphys. Sans and Alphys are both really smart and know all sorts of stuff about humans. And Sans maybe already knows they’re dead? He sometimes says stuff about how the ‘physical stuff doesn’t matter’ for them. And he probably definitely knows about time travel, which Frisk couldn’t do until they died, so it’s safest to just assume Sans knows everything. He usually does.

Sans knows stuff and doesn’t tell anyone anything, and Alphys kept the Amalgamates secret and Frisk might sort of be an Amalgamate maybe, with the coming back to life and all, so Frisk can be sure both of them can keep a secret. That’s important, because Frisk is gonna come clean. They’re gonna tell Sans and Alphys that they’re dead, and ask for help.

They don’t want their Mom to worry, and they don’t know how to stop her. They can’t just keep hiding it from everyone forever, not without help. And they don’t want to tell everyone yet, either. Not until they know what happened, or at least until they’re pretty sure they’re not gonna just drop dead again some time.

Sans and Alphys know things. Sans and Alphys can help them figure it out. And then, some day soon, Frisk will be ready.

Or dead.

Hopefully not dead.

* * *

Toriel waits anxiously by the tallest kitchen cupboard, which is what she has judged to be the least likely door in the house for any normal person to enter from. Sans will be bringing her child home soon, with Doctor Alphys, to discuss Frisk’s health. She is hoping to hear a knock-knock joke before he enters, indicating that Frisk is in good health. She is dreading silence.

The world goes dark, as it often does when Sans appears in places he is not meant to be, and when she can see again Sans is strolling out of the trapdoor to the attic, leading Frisk by the hand as he walks down the wall and to the floor. Doctor Alphys descends the ladder.

There was not a knock-knock joke. Toriel watches her child closely, but Frisk is quiet and holding onto Sans’s hand tightly. Sans is holding on just as much, watching them like he’s never seen a human before. It takes him a dazed moment to turn to Toriel.

He stares at her like he’s never seen her before, either. Or like he’s seeing her for the first time in a very long time.

“U-um. Y-your majesty? I-I’ve, um, we. I.” Alphys cowers under Toriel’s gaze, but recovers. “That is, th-the examination is complete. And! It’s all, it’s okay! I mean, Frisk is—not sick, or, h-hurt, or. Anything. There were, um, a few things that I wanted to f-follow up on, t-to see th-them, um, better, in more detail that is, because it’s important for being healthy, uh…”

She fiddles her fingers together and hunches over herself, at least self-aware enough to know that Toriel is not pleased to hear that Doctor Alphys would like to study her child.

“can we borrow the kid?” Sans asks.

“Excuse me?”

He looks between Toriel and Doctor Alphys, seeming to realize for the first time that a conversation is happening.

“oh. uh, nothing to do with the doctor stuff. i mean, kinda, i guess? anyway. me and paps. can we borrow frisk for a weekend? family road trip?” His tone is closer to pleading than Toriel would have thought him capable of, especially for an otherwise innocuous request. Perhaps this is how she sounded, when he made that promise through the door. Or perhaps he fears that she will be selfish and refuse to let Frisk go, even for a weekend.

“we learned that humans have skeletons in them today,” he says. “so they’re basically family. so they should come. we can cook ‘dogs and do skeleton family stuff. ‘cause they’re basically a skeleton. plus skin.”

Sans looks at her, and then away, and then at her again. It seems that he was very surprised to have learned this new information. He looks like his whole world has been tipped off its axis.

Toriel is, of course, aware that humans have skeletons—that used to be how skeleton monsters were born, long before the war.

For there to be skeletons around even now, she supposes they must have found some other way to reproduce. Some way that resulted in skeletons like Sans, whose fused jaw could only have been human if the lower half of his face had been smashed beyond repair and healed spectacularly badly; and Papyrus, whose wonky left eye socket would only be possible for a former human if some truly inexperienced monster tried to over-heal it and ended up growing bone over where part of the socket was meant to be.

No, skeleton monsters much have mutated since she entered her self-imposed exile. Those few who were left must have found another way to carry on their legacies, resulting in less-human skeleton monsters.

Still, humans and skeletons are a distant sort of family. She’d been under the impression that Sans and Papyrus were aware of that. Papyrus had mentioned something to that effect before. But perhaps Sans hadn’t known before Alphys or Frisk told him, or simply hadn’t thought of it in relation to Frisk.

Either way, Toriel can’t see the harm in Frisk getting to know their friends as distant cousins, as well as trusted companions. And Sans certainly wouldn’t be suggesting the trip if their safety was at risk.

“Of course you may,” Toriel grants. “if, Frisk, you wish to go?”

Frisk is nodding before she gets halfway through the question. “Sans is teaching me blue magic.”

Ah. ‘skeleton family things.’

Toriel blinks, surprised—she knew Sans must be younger than the Barrier, but she’d anticipated that it would be generations on the Surface before a single monster was willing to teach any magic to a human; even magic that had nothing to do with barriers at all.

Frisk sounds eager, as much as Frisk ever does, and when they shift to bump Sans with their full weight like an affectionate cat, he doesn’t dodge them. Surprised she may be, but she cannot fault Sans for his choice in students.

Sans must read her startlement in her face, because he corrects, “ _about_ blue magic. i’m teaching you _about_ blue magic. i dunno if you can even use magic with your SOUL thing. you might overpower it and blow up half the countryside. so, y’know. road trip. keeping collateral down. if that’s ok with your mom.”

He shrugs, dismissing their powerful human SOUL and the potential destruction it could cause like a slime trail left by a Moldsmol. Irritating, but a part of life. The part that one must occasionally take weekend-long trips out of town to accommodate, if one is to teach a human child magic after only just escaping a human-constructed magical prison.

And he calls Toriel Frisk’s mother. Always, without question or hesitation—as if it is perfectly natural that a Boss Monster can raise and cherish a human child, despite humans’ and monsters’ ragged history. Even though eight of her children, seven of them human, have died, most of them violently and alone; Sans will say without hesitation that she is a mother, and even a good one. Toriel is not certain that she deserves his faith, and will likely never know how she earned it, but she cherishes it just the same.

This is how Toriel knows she was right to trust Sans. He treats Frisk as a human, but not as if their humanity is foreign and frightening. Perhaps there is something to that kinship, after all.

Alphys, Sans, and Frisk all look to her for her yes or no.

“Please?” says Frisk. “I wanna learn. We’re family.”

Her child, who came to Mt. Ebott for reasons that Toriel knows better than to ask for, clings to her dear friend like he is something long-lost and ached for.

Sans, who speaks about his family with every other breath, but can’t count anyone in it but Papyrus. Who hangs out in Toriel’s home at odd hours just to check that Frisk is safe and well. Who speaks to Frisk when Toriel can’t, and finds them when they’re missing.

That Sans allows Frisk to hold onto him, subtly adjusting his slouch into something a little more supportive, with a particular softness to him that Toriel only sees from him with Frisk and Papyrus.

Family.

Toriel allows herself to think that perhaps some human blood relative will not swoop in and steal Frisk away.

Perhaps this will be enough for them—a mother who loves them; a family whose genealogy they can’t trace but who they do belong with, as deeply as their bones. Who is willing to claim them and teach them as one of their own.

Perhaps Frisk will not resent her for stealing them away from their people, keeping them, raising them as her own. Perhaps, with the help of her own loved ones, Toriel will do right by this one surviving child.

“Of course,” Toriel says again, warmly. “Of course, my child. How could I say no to family?”

**Author's Note:**

> sans: im dead inside  
> Alphys: you're dead on the outside too  
> sans: what  
> Alphys: what  
> Frisk, entering stage right: I'm dead too we should start a club
> 
> so who called that sans and papyrus were literal undead? This story was secretly a challenge for How Many Times Can I Say Sans Is Dead Before People Start Noticing. :D


End file.
